The invention relates to a luminaire comprising:
a concave reflector with a plane of symmetry and an optical axis having an optical center lying in the plane; PA1 a light emission window tangent to the reflector and transverse to the plane of symmetry; PA1 holder for accommodating an electric lamp transversely to the plane of symmetry, with an elongate light source of the lamp in the optical center and; PA1 a light-reflecting screen extending along the optical axis, transverse to the plane of symmetry; and reaching up to in the light emission window,
the reflector comprises several plane facets which in their widths w are bounded by first, mutually substantially parallel, substantially flat planes perpendicular to the plane of symmetry, and which in addition in their lengths l are bounded by second substantially flat planes which arrange the facets into rows which extend along the plane of symmetry.
Such a luminaire is known from U.S. Pat. No. 5,544,030.
The known luminaire is not only symmetrical in the plane of symmetry, but substantially also in a plane perpendicular thereto and passing through the means for accommodating a lamp. The luminaire comprises a large number of mutually parallel second flat planes which bound the facets. The reflector is tangent to the light emission window around the optical axis, and the optical axis is perpendicular to the window. The luminaire is capable of concentrating light generated by an accommodated lamp into a substantially symmetrical light beam.
The luminaire may be positioned with its optical axis pointing obliquely downward. A screen is provided in the space defined by the reflector above the optical axis. The screen thus intercepts all light beams originating directly from the lamp which would be radiated in upward directions if the screen were absent.
The known luminaire is accordingly suitable for use inter alia in the illumination of grounds, for example sports grounds, because the luminaire counteracts the radiation of stray light, i.e. light not directed at the grounds to be illuminated. Irregularities in a transparent plate closing off the light emission window, however, or pollution on this late may nevertheless give rise to unpleasant stray light which is directed horizontally or upwards, as may light reflected by the plate towards the reflector.